Objectives: Fractures have serious health consequences including lengthy rehabilitation and the most serious, hip fractures, may cause prolonged or permanent disability and almost always require hospitalization and major surgery. We have engineered a bio-active silica based nanoparticle capable of promoting osteoblast differentiation and mineralization while inhibiting osteoclastogenesis. Furthermore, we have identified a potential key intracellular regulator of the effect in autophagy as well as key signaling pathway in NF-?B. These nanoparticles have the potential to promote new bone formation while simultaneously reducing bone breakdown. Research Plan: Our preliminary studies have identified the cellular process of autophagy as a potential key mechanism by which our nanoparticles differentially alter cell function in osteoblasts and osteoclasts. Autophagy is a highly regulated cellular process that can be induced by various stimuli, such as stress, cytokines, pathogens, aggregated proteins, damaged or surplus organelles that are ultimately degraded. Although only partially understood, autophagy has been linked to controlling cell signaling by targeting the proteasome and restricting inflammation through limiting the IKK/NF-?B pathway. Based on these studies we hypothesize that our engineered nanoparticle represents an agent capable of preventing and/or reversing age- related bone loss by stimulating autophagy in osteoblasts and osteoclasts. Methods: To test our hypothesis we will utilize we will utilize in vitro models of osteoblast and osteoclast differentiation and function to investigate the mechanism(s) by which our nanoparticles alter function. We will investigate the effects of nanoparticle induced autophagy on NF-?B signaling. We will utilize a model of aged induced osteoporosis to determine the effect of our particles in both promoting bone volume and blunting bone loss. Endpoints include a quantitative and qualitative analysis of bone and serum factors while ex vivo studies will address the effects of our nanoparticles individually on osteoblasts and osteoclast in vivo. Clinical Relevance: Fractures have serious health consequences including lengthy rehabilitation, prolonged or permanent disability, and hip fractures almost always require hospitalization with associated major surgery leading to increased morbidity. Prevention of fractures will greatly reduce both the personal and financial burden to veterans relative to post-fracture treatment. The development of anabolic agents that can promote the rebuilding of lost bone mass would represent a significant impact on the field and on the treatment of bone disease. No current FDA approved agent is able to achieve this and the benefits of a novel therapeutic agent to supplement, or even replace, current therapies for patients suffering from either naturally occurring or disease associated bone wasting.